The embodiments relate to dentifrice compositions containing minor amounts of relatively small particle size high cleaning abrasives, without antibacterial agents, fluorides, and other oral care actives. In particular, dentifrice compositions having good stain removal characteristics. The dentifrice compositions can be in the form of encapsulated compositions, solid confectionary compositions, gums, and the like, which optionally may be positioned within the bristles of a tooth brushing device.
Conventional abrasives include silica, for example in the form of silica gel, hydrated silica or precipitated silica, alumina, insoluble phosphates, calcium carbonate, resinous abrasives such as urea-formaldehyde condensation products and the like. Among insoluble phosphates useful as abrasives are orthophosphates, polymetaphosphates and pyrophosphates. Illustrative examples are dicalcium orthophosphate dihydrate, calcium pyrophosphate, β-calcium pyrophosphate, tricalcium phosphate, calcium polymetaphosphate, sodium tripolyphosphate (STPP), tetrasodium pyrophosphate (TSPP), and insoluble sodium polymetaphosphate. One or more abrasives typically are present in a dentifrice in an abrasive effective total amount, typically 5% to 70%, for example 10% to 50% or 15% to 30% by weight of the composition. The average particle size of an abrasive is generally 0.1 to 30 μm, for example 1 to 20 μm or 5 to 15 μm.
Synthetically produced silicas play an important role as an ingredient in many of today's toothpaste formulations. Such silicas are relatively safe, nontoxic, ingredients which are compatible with other toothpaste ingredients, including glycerin, sorbitol (or xylitol), thickening agents, detergents, coloring and fragrance materials and optionally fluoride and other actives, whereby the silica acts as an abrasive to clean teeth, remove plaque and food debris.
As an abrasive, silicas debride and physically scrub the external surface of the teeth. This scrubbing action removes the organic film (i.e. the pellicle), formed of salivary proteins which covers the teeth and which is known to become stained and discolored by foods, such as coffee, tea and berries, as well as, by tobacco smoke, cationic antibacterials, and chromogenic bacteria. Such physical removal of the stained pellicle is a simple and effective means of removing the undesirable surface staining and discoloration which occurs daily. Further, such physical removal of the pellicle also removes plaque bacteria on the pellicle surface.
Synthetic silicas include both silica gels and precipitated silicas which are prepared by the neutralization of aqueous silicate solutions with a strong mineral acid. In the preparation of silica gel, a silica hydrogel is fanned which is then typically washed to low salt content. The washed hydrogel may be milled to the desired size, or otherwise dried, ultimately to the point where its structure no longer changes as a result of shrinkage. When preparing such synthetic silicas, the objective is to obtain abrasives which provide maximal cleaning (i.e. removal of stained pellicle) with minimal damage to the tooth enamel and other oral tissue. Dental researchers are continually concerned with identifying synthetic silicas meeting these objectives.
U.S. Pat. No. 4,153,680 and GB Patent Application 2,038,303A both disclose the general use of silica hydrogels or hydrated silica gels as dentifrice polishing agents. U.S. Pat. No. 4,632,826 discloses the use of hydrated silica gels in combination with a weakly calcined alumina polish, to form a combination abrasive system. U.S. Pat. Nos. 4,943,429, 5,176,899 and 5,270,033 provide lists of alternative polishing agents, such lists including hydrated silica gels.
U.S. Pat. No. 5,939,051 discloses dentifrice compositions prepared with silica gels having low abrasion and high cleaning products. However, the silica gels have a low particle size distribution of from 2 to 4 microns in order to achieve the low abrasive properties. Manufacturing such small particle size silica gel is energy intensive and relatively costly.
U.S. Pat. Nos. 5,658,553 and 5,651,958 disclose dentifrice compositions containing a combination of precipitated silica and silica gels having high cleaning and low abrasion as indicated by their low radioactive dentin abrasion (RDA) values. Due to the low abrasive nature of the silicas described in U.S. Pat. Nos. 5,651,958 and 5,658,553 the composition inherently has limited cleaning ability.
RDA value is a dental art recognized method of determining the abrasiveness of dentifrice formulations and is determined according to the method recommended by the American Dental Association as set forth by Hefferren, Journal of Dental Research, Volume 55, Issue 4, July-August 1976, pp. 563-573, and described in the Wason U.S. Pat. Nos. 4,340,583, 4,420,312 and 4,421,527.
It is known in the dental art that increasing the RDA value of a dentifrice composition above 110 does not result in a corresponding increase in the cleaning performance of the dentifrice, as measured by Pellicle Cleaning Ratio (PCR), an in vitro method used to measure the efficacy of removing tea and coffee tooth stains relative to a standard. The PCR values referred to herein are obtained by a modification of the method described in “In Vitro Removal of Stain with Dentifrice”, G. K. Stookey, et al J. Dental Research, 61, 123-9, 1982. The modification of the PCR method used herein is described in U.S. Pat. Nos. 5,658,553 and 5,651,958. In this modification, a clear pellicle material is applied to a bovine tooth first, which is then stained with a combination of the pellicle material and tea, coffee and FeCl3 whereas in the original method described by Stookey et al, both pellicle and stain are applied simultaneously.
Silica particles referred to as “high cleaning” silica are known and described in, for example, U.S. Pat. Nos. 7,306,788, 7,267,814, 6,896,876, 6,669,929. Many of these are commercially available from J. M. Huber (Havre de Grace, Md. USA), sold under the trade name Zeodent™. Other silicas are designed to replace a portion of conventional silicas to enhance or boost their cleaning efficacy, as described in, for example, U.S. Patent Application Publication Nos. 2009/0010973, 2006/0008423, 2006/0008422, 2005/0129628.
Dentifrice compositions in the form of solid, semi-solid, or encapsulated compositions positioned within the bristles of a tooth brushing device are known. Colgate® WISP™ is one such device. The Wisp device is a small tooth brushing device (about 8.9 cm (3.5 inches)) in length) that includes a gelatin encapsulated liquid composition positioned within the bristles. The liquid capsule releases a burst of freshness when used, without the need for water or rinsing. The Wisp is designed to be used once, and then discarded.
There remains a need to provide a dentifrice composition that is not necessarily intended to be used as a toothpaste or gel, that does not necessarily contain oral care actives, and that is effective in removing stains and cleaning teeth.